I dont know either. Neat idea!
Yes, this issue has been discussed her a lot. And no one seems to have the definitive answer, maybe because water in YOUR area is slightly different in the minerals it contains. What is working best for me now is a mixture of plain white vinegar, lemon juice and water. I spray it on, and let it sit for a while, as I do other things in the bathroom. I use a Magic Eraser to scrub the stinky vinegar stuff off. Then spray on ordinary ammonia based glass cleaner and wipe it down with a clean lint free cloth.
I am always open to new ideas for this problem!